1. Remove the `versioned_value::factory` class, it didn't add any value. It just
forced us to create an object for making `versioned_value`s, for no sensible
reason.
2. Move some `versioned_value` deserialization code (string -> internal data
structures) into the versioned_value module. Previously, it was scattered all
around the place.
3. Make `gossiper::get_seeds` const and return a const reference.
I needed these refactors for a PR I was preparing to fix an issue with CDC. The
attempt of fixing the issue failed (I'm trying something different now), but the
refactors might be useful anyway.
* kbr--vv-refactor:
gossiper: make `get_seeds` method const and return a const ref
versioned_value: remove versioned_value::factory class
gms: move TOKENS string deserialization code into versioned_value
be5d3f4733